Up to now, sensors using a field-effect transistor have been known widely (Japanese Patent Application Laid-Open No. S56-76043). Among them, plenty of attempts to enhance measuring sensitivity to a detection object material by forming a nano structure on a sensitive section of a field-effect transistor have been done. For example, a sensor is disclosed, the sensor in which a nano structure (a structure constituted by a plurality of material particles (clusters)) was formed in a sensitive section of a field-effect transistor, so as to raise the mechanical fixation of biogenic substances (a cell, a receptor, gamma-globulin, etc.) to a sensor sensitive section, and further, to enhance a signal transmission characteristic and measuring sensitivity (Japanese Patent Application Laid-Open No. H10-185864). Specifically, this is structured so that an active contact surface of the sensor may mostly coincide with a contour shape of the outside of each biogenic substance.